Ask HN: Hackers locked my dad out of WhatsApp – need advice

So about 5 hours ago someone managed to transfer my dad's WhatsApp account to another phone. We're currently locked out of phone and SMS verification because this has been requested too many times. I know this is a bit of a long shot, but does anyone know who I could contact to find out what is going on? I'm really worried that they might be trying to collect PII on him to mount a social engineering attack in the future.